The war over genetically modified organisms rages on in Washington state, and the big money may be winning the current battle.

On November 5, Washington state will vote on a new ballot initiative that will require companies to label food products that contain genetically modified organisms (GMOs). The measure, known as I-522, has recently seen support dwindle as major corporations spend millions of dollars on anti-labeling advertisements. A consortium of major food, agriculture, and chemical companies, including DuPont (NYSE:DD), General Mills (NYSE:GIS), Monsanto (NYSE:MON), Nestle (OTCMKTS:NSRGY), and PepsiCo (NYSE:PEP), have spent nearly $22 million on campaigns against the bill. Pro-labeling supporters, on the other hand, have spent only $6.8 million on advertisements.

The corporate spending has been fast, furious, and apparently, effective: In September, one poll showed support for I-522 leading the opposition by a substantial 45%. A month later, a survey released by non-partisan public opinion research group The Elway Poll found that support lead opposition by only four percentage points.

Opposition to the bill has also received critical support from the Grocery Manufacturers Association (GMA), which has raised approximately $11 million to fight labeling. The group, which represents more than 300 food companies, has argued that GMO labeling would end up costing the consumer. As GMA spokesperson Brian Kennedy said in a statement, "It [the bill] would require tens of thousands of common food and beverage products to be relabeled exclusively for Washington state unless they are remade with higher-priced, specially developed ingredients. The measure will increase grocery costs for a typical Washington family by hundreds of dollars per year."

Supporters of the proposed legislation argue that GMO labeling would be valuable to consumers, allowing shoppers to make informed and healthy choices that they might not otherwise make. They cite hundreds of studies related to GMO crops and human and animal health. (Many scientists have also argued that such studies are inconclusive.) Moreover, they argue that GMO crops encourage practices that lead to environmental problems, such as the use of agrochemicals and pesticides.

In the 2012 election in California, a similar labeling measure failed to pass; 51.4% of voters were against the proposition and 48.6% supported it.

However, some advocates for the bill, like David Bronner, the president of California-based Dr. Bronner's Magic Soaps, sees the fight for GMO labeling continuing up to the federal level, even without a win in Washington state (Bronner has contributed $1.7 million to the pro-labeling campaign).

As he said to the Huffington Post, "We're in this for a long haul. Even if we lose here we're still feeding the national debate and conversation. We'll get it eventually."